Fluid drive mechanism



2 Sheets-Sheet l April 10, 1956 F. w. MARSHALL FLUID DRIVE MECHANISM Filed May 2l, 1954 FPA//d//V Hf. MARSHALL MQW@ April 10, 1956 F. w. MARSHALL 2,741,092

FLUID DRIVE MECHANISM Filed May 2l, 1954 2 Sheets-Sheet 2 United States Patent 2,741,092 FLUID DRIVE MECHANISM Franklin W. Marshall, Pittsburgh, Pa.

Application May 21, 1954, Serial No. 431,415

7 Claims. (Cl. S0- 52) This invention'relates to a uid drive mechanism. More particularly the invention relates to a hydraulic operating mechanism as applied to a hospital bed which has adjustable head, knee and foot panels which are movable up and down to adjust the panels to various positions to make a patient on the bed comfortable.

Nursing attendants are not always available to make adjustments of a hospital bed. It is desirable that a patient may be able to easily make the desired adjustments of the bed panels while the patient is on the bed.

Experience has shown that the bed panels should be positively raised and lowered and that the motion should be slow and smooth to aid the patient in iinding a comfortable position. It is important also that the raising and lowering movement should be limited and when a desirable'adjusted position of the panels is found, that the panels shall remain lixed in that position until a changed position' is desired.

For patients who have heart trouble or trouble with the blood circulation, it has been found that such patients can obtain great relief by having the feet elevated while lying on his back. The natural tendency is for the knees to be raised as the feet are raised but the medical profession has found that it is very desirable to have independent as well as coordinated adjustment of the knee and foot panels to obtain the maximum benefit for a patient.

It is important to have a bed panel adjusting mechanism that is simple to operate with the minimum number of parts and to be dependable in its operation.

Another important feature for a hospitalbed is to provide a panel adjusting mechanism which is quiet in its operation to avoid annoyance to the patientV operating the .panels and other patients in a hospital.

` The primary object of the present invention is to provide a uid drive mechanism for obtaining a positive reciprocating motion with control means for stopping and starting the motion and for positively holdingV the Y moving part in any desired adjustedposition.

Another object of the invention'is to provide a fluid operating mechanism for a hospital bed having adjustable head, knee and toot panels by which the panels may be independently adjusted and locked in adjusted position.

Another object of the invention is to provide an electrical control or" a uid operating mechanism for adjustable head, knee and foot panels of a bed by which 2,741,092 Patented Apr. 10, 1956 rice anism herein illustrated and described Aand particularly defined in the appended claims.

The various features of the invention are illustrated in the accompanying drawings in which:

Fig. l is a plan view with parts omitted yof the adjustable panels of a hospital bed having the improved iiuid operating mechanism applied thereto;

Fig. 2 is a view in side elevation of the bed panels and the fluid operating mechanism shown in Fig. l;

Fig. 3 is a detail view in elevation of the limiting switch mechanism for coordinating the operation of foot and knee panels;

Fig. 4 is a double throw electric switch by which operation of the head panels may be controlled;

Fig. 5 is a diagrammatic view of the fluid operating mechanism showing the cylinders for operating each of the bed panels, the piping connections between the pump and the cylinders and the valves in the piping connec- Vtions for controlling the operation of the cylinders;

Fig. 6 isa Wiring diagram showing the electrical arrangement for operating'the fluid pump and the valve operating solenoids; and

all adjustments and the holding ofthe panels in a de- Figs. 7 and 8 are diagrammatic views of a four way valve to be used alternatively for the four valves for each of the cylinders as shown in Fig. 5.

The fluid operating mechanism of the present invention has many applications where a reciprocating motion is desired with controls for stopping and holding a moved part in any desired position. The application of the huid operating mechanism to the head, knee, and foot adjusting panels of a hospital bed is shown in Figs. l and 2. rI'hese drawings show only the deck portion of the bed. This deck portion is made up of a head panel lll which is pivotally connected with a tiredv panel 11 by pivots 12. A knee panel 13 is pivoted at the rear side to the fixed panel 1l by pivots 14 and at the frontend to the foot panel 15 by pivots 16. These panelsV are covered by a woven wire spring, the character of which is shown at 17 in Fig. l. This spring continues from the front end of the head section to the back end of the foot section as a continuous sheet and is connected to the panels by springs 18. The panels are pivotally movable with reference to one another and the spring sheet is general-ly covered by a sponge rubber mattress which contains a large number of cavities on one side which permits the mattress to bend and `ex with the spring sheet when the sections are adjusted at different angles in order to assume a position on the bed deck which is comfortable for a patient on the bed.

The head panel is moved about the pivots 12 by means of a hydraulic piston Whichis operated in a cylinder 19. The cylinder is pivotaliy connected at 2d to a frat-ne member 21 (Fig. l). A piston rod connecte/l to the piston in cylinder 19 is pivotally connected to an arm 23 ixed on a shaft 24 which is journaled between frame members 25 at opposite sides of the bed. Another pair of arms v25 which are iixed on Vopposite ends of the shaft 24 are connected by links 27 with the head panel by'pivots 28. When the piston in the cylinder 19 is reciprocated the head panel is moved up and down to the positions illustrated in solid and dash lines (Fig. 2). The arms 26 and links 27 support the head panel in a horizontal position when the piston is moved to a down position to place the .spring sheet in a substantially horizontal position.

The fixed section 11 is attached to the side rails 25 of the bed as shown in Fig. 2 and supports the rear` end of the head panel and the front end of the knee panel at the normal horizontal level of the spring sheet.

The knee panel is moved up and down by means of a piston in a cylinder 29 which is pivotally connected to` the frame member 21 by a pivotal connection 30 (Fig. 2).

A rod 31 connected to the piston in cylinderj29 is Vconnected with an arm 32 which is xed upon and rotates with a shaft 33 (Figs. 1 and 2) which is journaled between-the bedvirarnegside members 25. Arms 35 iixed Von opposite ends of the shaft33 Iare'pivotally connected with linksthat are ,pivotally connected attheir upper ends to the rear end of the knee section. Whenthepiston in the cylinder 29is reciprocated the shaft 33 is rotated and through ar-rns 35 and links 36 theY knee section lis raised and lowered. Y

'Ihe foot panel 15 has no'direct connection with the power drive mechanism vbut is moved upY and down by meansfof apradlel which is pivotally connected at 38 (Eig. l2) to downwardly extending frame members 39 secured to the bed frame members 25.

Cradle V37 is composed of normally horizontal guide arms l-which are connected together by rod 4i. To the Ahorizontal' arms are connected inclined cam arms 42 which extend down to a level below the bed frame and are connected to pivotal :arms 43 which have the pivotal connection 38 with the bed frame. VBracing rods 44.are connected between the guide arms 4G and pivotal arms 43 to make the cradle arigid unit structure. The cradle is given an oscillating .movement,

'for theV purpose of raising and lowering the foot panel, by means of a piston in a cylinder 45. The front end of the cylinder 45 is connected by means of supporting rods 46 with the rear of the bed frame. The piston rod 47 is adjustably connected with an axle 4S which is mounted on rails Y49 by means of trolleys or rollers 59 at each end of the axle. The rails 49 are secured to the bed frame. The axle 4S also has rollers 51 which ride under the cam rods 42 of the cradle, and as the axleis-moved toward the head of the bed by reciprocation of the piston in the-cylinder 45,-the cradle is oscillated to raise the foot panel. When the foot panel is raised, rollers 52 (Fig. 2) onV the rear end of the foot panel .ride along the horizontal bars 48 of the cradle. Y

The details of the operation of the hydraulically operated cylinders 19, 29, and 45 are illustrated diagrammatically in Fig. 5. These diagrammatic cylinders are given the same numeral as that shown in l; This diagram illustrates the piston in the cylinder 19 and the valves for that'cylinderposition ready to receive a pressure fluid at the front ends of the cylinder for raising the head panel of the bed deck. The valves for cylinders 29 and 4S, of `Eig. 5 are in a neutral position to which they are vmovecl by springs 94 of operating solenoids when the electrical current is cut olif-'from the solenoids. Each cylinder is a double-acting cylinder in that piping connections 53 and 53' are connectedat opposite ends of the Ycylinder by which tluid'under pressure maybe introduced for the purpose of driving the piston in opposite directions. The pressure uid is delivered from a pump 54 operated by Van electrically-driven motor 55. The iluid under pressure ows throughV a supply line A5,6 past a check valve 57, thence through a control valve 58 to the cylinder. Each of the cylinders 19, 29, and have the in the pressure supplyline, and hold the pistons in fixedV position when the valve operating solenoids in the cyl-V inders are disconnected from electrical current. Preferably compression springs of a predetermined compression strength are located at each end of the cylinders 19, 2 9, and 45 to limit the reciprocating motion of the piston within the cylinder. When the piston moves into contact with ,the springs at the ends of the cylinder, the fluid pressure developed by the pump 54 is vmaintained substantially uniform'by means of a relief .valve 59 operated by a spring 6,0 topermit Yfluid to pass through 'aline ,6,1 and line 62V to a return Yline 63 and thence to a .sump

-which in turn are connected with the cylinders.

.64. Whenuidisintroduced vto Ythefrontends `v.65 V ofthe cylinders to move the pistons, iluid is returned from the rear end of the cylinders through a line 53', thence through a valve 58' to a line 66 connected with all of the valves When the pressure uid is introduced into the front end 65 of the cylinders, the panels of the bed deck are raised and will be held in the raised position by the check valves 57 so long as the patient in thefbed desires to have them in raised position. When it is` desired to change the position of the panelsV of thebed deck, an electrical switching apparatus as hereinafter described is operated to shiftY the position of the valve channels to .introduceV pressure tluid into the rear end 'of the cylinders and exhaust fluid from the front end of the cylinders through the valve. When the valves are shifted, the tluid under pressure will be introduced into the rear end of the cylinders and the pistons will be .positively driven to lower the bed panels under a controlled operation of the cylinders. Since each of the fluid supplyA lines'has -a check Valve, the bed panels will be locked in any adjusted position while rising or whilebeing lowered, andif the motorA continues to supply tluid to the supply line when the pistons 'reach the end ofthe reciprocatingmovement, the relief valve 59 will permitthe'tluid delivered by thepump to return to the sump 64. Inorder to avoid any stoppage of .the

valves or pistons, theoil or pressure iluid drawn from the sump 64 by the pump 54 is passed through aiilter/68. At the time a switch is `operated to stop the operation of a panel, the valves 58 and 58 of the cylinder 'being controlled willbe shifted to a neutral positionV by springs 94 to cut off the return of uid :from the hydraulic cylinder to the sump 64. l

In the normal operation of the bed panels,rthe up and down-movement ofthe panels by means of the hydraulic v cylinders is not limited, except at the time that the pis-V `As shown in Figs. 1 and 3, a cam arm 69 is mounted on the axle 48 and projects rearwardlytoward the rearl end Vof the foot panel. A cam 70 is xed on the shaft 33 for operating vthe knee panel and bears against a lever 71 Vwhich vis lpivotally connected to the guide frame 49 by a pivot '72. The Yfront end of the lever 71'carries electrical switches 73 and 74 which vcontrolthe electrical circuits for operating the `cylinders. 29 and 45.` The switches 73 and `74 have rollers 75 which bear against an inclined cam face 76 on the cam 69, and during the v normal operation of the foot and knee panels, thecams 70 and 76 are so shaped that the rollers 75 do not bear f p against the cam face 76 to keep the electrical'circuit closed. As shown in the drawings, the electrical circuits controlled by the switches 73 and 74 will be closed so long as the surface of the panels 13 and 15 make a straight angle, but if the knee panel were to be de pressed below the .level of the surface of the foot panel,

then'the guide roll of the switch 73 will-contact the 'cam` knee panels, iboth panels will be cut out ,of .Operation until the angular position between the panels is adjusted.

The ,condition discussed` above can only occur during Y' the downwardmovement .of the knee section, and if the limiting switches 73 and 74 are operated to break the circuits, then it will be necessary to raise the knee panel to adjust the angular position before either-of the panels may be adjusted further in a downward course.

The wiring diagram for operating the pump motor and the switches for controlling the ow of liquid through the hydraulic cylinders is illustrated by the conventional wiring diagram (Fig. 6). Switches 77 are used for controlling the upward movement of the panels, and switches 78 are used for controlling the movement of the panels downwardly. When any of the switches 77 are put into operation, arms 79 are brought into contact with points 80 which connect a line 81 to one terminal of a power circuit 82. The closing of the switch also brings current from the power circuit 82 through the line 83 and a relay 84 back to the line 85. The relay thereupon closes the circuit 86 of the motor 55 to start the motor, and at the same time current ows through solenoid 87 for operating valve S8 for directing pressure uid at the rear end of a cylinder back to the sump. The valve 58 will be at this time in position to supply pressure uid to the front end of the cylinder because the valve 58 was placed in this position by a spring 94 whenfthe electrical current was cut oft" of the operating solenoid. Three vcylinders are illustrated in the drawing, and three separate switches are used, one switch for each cylinder. The electrical control of the pump and valves for each cylinder is the smc. The operation of the down operating switches 78 is connected through the circuit so that when the switch is moved to contact the points 88, at the bottom of the diagram, the lines 81, 83 are closedrto rst start the motor 55 before solenoid switch 89 is operated to shift the valve 58 to exhaust fluid from the front end of the cylinder to the sump. The valve 58 of this cylinder, while'in neutral position, made a connection to supply pressure uid to the rear end of the cylinder.

Preferably the switches used for operating the circuits are three position switches such as illustrated in Fig. 4.V

In normal position the switch arm 90 stands in a vertical position, being held in this position by spring arms 79 thatform one side ofan ,electrical circuit, When the switch arm 90 is moved to the right, a contact point 80 will be connected with an arm 79 to close an electrical circuit 81-83 for operating the pump and the circuit for operating one of the solenoids 87 to shift valve 58. When the arm 90 is moved to the left, an arm 79 will be moved to the position Vto make a contact with a circuit contact 88 to close the motor circuit and the circuit to operate solenoids 89 to shift valve 5S. In the assembled form of the switches of Fig. 4, the switch members 77 and 78 will be mounted side by side so that a movement of switch arm 90 to the right will close two circuit contacts 80 for an up movement of the panels. When arm 90 is moved to the left, two contacts 8S will be made for downward movement of a panel.

In Figs. l and 2 is illustrated the arrangement of a switch box 93 with three switches therein so that arms 90 extend out of the box. The switch box is pivotally mounted on aside rail 25 of the bed so that it may be moved up into position to be readily available for operation by a patient with the patient lying on the bed. The switch arms 9B may be moved to up or down adjusting positions in order to set the panels in any desired angular position for obtaining a comfortable position of the patient on the panels. When the switch arms are released, the switch will move to a neutral position, and the movement of the panel will cease.

The valves 58 and 58' illustrated in Fig. 5 are four-way valves which are operated by solenoids such as solenoids 87 and 89 illustrated in Fig. 6. When the switch arm 90 sets valves 58', for example, to exhaust pressure liuid from the back end of a cylinder to the sump for an up movement, the valve 58 had been previously set to supply pressure uid to the front end of the cylinder. Vice versa when the switch arm is operated to set valve 5S to exhaust pressure uid from the front end of the cylinder, the valve 58 had been previously set to supply pressure uid to the rear end of the cylinder. At any time that the switch arm 90 is released, it is moved to a neutral position by spring arms 79, the electrical circuit is opened and springs 94 move the valves 58-548 into a position to connect both ends of the cylinder to the lines 53 andSS which are closed by thel check valves 57.

In Figs. 7 and 8 are illustrated two positions of a fourway valve which may be used for the two valves 58 and 58 that are used with the fluid operated cylinders illustrated in Fig. 5. The valveof Figs. 7 and 8 is illustrated as a rotary mounted plug type valve having four channels therein for conducting uid to and from the piston operated cylinder. Solenoids 95 and 95 are Vmounted at opposite ends of the valve for the purpose of rotating the valve through an arc of approximately 45. The sole,-v

noid 95 may be mounted in the circuit illustrated in Fig. 6 to take the place of solenoid 87 and would be operated only when switch 77 is closed. The solenoid 95 would then be connected with switch 7%V to be operated only when switch 7S is closed. In one position of the valve (Fig. 7) as set by the solenoid 95, diametrically arranged channels 96 will introduce pressure liuid from pump 54 to the front end of a cylinder while exhausting fiuid from the other end of the cylinder to a sump 64. When the current is cut olf, springs 97 and 98 engaging the solenoids will move the valve member into a position to close all ports into and out of the valve. When solenoid 95 is operated the valve plug will be rotated about 45 in a direction opposite to the rotation made by solenoid 95 to setthe valve as shown in Fig. 8 to deliver pressure fluid from pump 54 through diagonal channel 99 to the rear end of the cylinder while exhausting fluid from the front end of the cylinder through diagonal channel 10i) to the sump V64. With this arrangement therefore the four-way valve which would be connected in the supply line and the return line will serve the functions of the four-way valves 58 and 58' and the two check valves 57.

The normal operation of the bed panels may be carried on by a patient who is convalescing. If it is desired that the panels should not be adjusted by the patient, then a switch in the main electrical circuit 82 may be opened and A controlled only by a nurse, and thereby leave the adjust- 'ment of the bed panels to a nurse. vThe desirable feature of the present invention, however, is to supply the electrical power to the switch box 93 so that the patient may be able to adjust the panels of the bed without calling upon anurse. Y I

From the construction described above, it will be apparent that each of the panels may be operated independently of the other. The panels may be moved up and down simultaneously. Further, one panel may move up while other panels are moved down. A limiting control is used with reference to the downward movement of the knee panel in order to prevent the knee and foot panels from being placed into an angle which is uncomfortable and should not logically be used.

It will be apparent furthermore Vthat the uid drive mechanism which is illustrated and described herein has a wide variety of uses in that it can positively move a desired member through a reciprocating movement and hold the moving member into any desired position by the mere operation of a single control switch.

As shown in Fig. 6 the arrangement of the switches 77 and 78 is to close the motor operating circuit in advance of closing the solenoid Valve operating circuit. These switches may be directly connected with the power circuit to simultaneously close both a motor operating circuit and a valve operating circuit so that the relay and its motor circuit closing switch would not be required.

The preferred form of the invention having been thus described, what is claimed as new is:

1. A uid drive mechanism comprising a cylinder with t channel-for connecting "the supply line With'the cylinder and a channel for connecting the'cylinder with a return line leading to the sump, an electrical circuit 'for the solenoid valve arranged to position'the valve to supply pressure Vfluid to one end of the cylinder while-exhausting uid from the other vend of the eylinder,-said 'electrical circuit being connected with the pump motorby a relay in series therewith 4to drive 'thefmotor and operate -a solenoid valve, and a switch in saidcircuit for selectively operating Ithe solenoid'controlvalve to lcorrtioi the direc- Y tiontof movement of the piston. I

2. The fluid drive mechanism -defined in Vclaim l in which `the'electrical circuit starts the motor in advance of the closing of the relay circuit 'for operatingfthe control valves.

Y 3. A fluid driveV mechanism comprising `a cylinder with a piston mounted to reciprocate therein, 'a `fluid supply line at each end of the cylinder, a'checlr valve in earch of,

the uid vsupply lines constructed -to permit liquid o'w in the direction of supply to a cylinder only, a sump, an electrically driven motor pump connected with the sump to introduce fluid under pressure to the supply lines, a uid return line extending from each end ofthe cylinder to the sump, a four-way solenoid operated valve vhaving a separate lport for registration with a line connected to each end of the cylinder, diametrically arranged delivery ports in the Valvetarranged to'cornrnunicatc-with the rst-V mentioned ports with one delivery vport being connected with a pressure fluid line vwhen Vthe other'delivery lport is connected with Vthe sump, a vvalve body in the valve having channels to connect the cylinder and delivery ports whereby uid vunder pressure may be directed against either side of the cylinder piston while-fluid is being vconducted away from the end of the cylinder opposite the end where pressure fluid is introduced, electrical circuits for operating the valve solenoids to selectively set the valve channels Vto control the movement of lthe cylinder piston, and means to adjust the valve body to connect the lines at each end Vof the cylinder with the uld supply lines when the electrical current to the valve solenoids is cut off.

4. The fluid drive mechanism dened in claim 3, in which a three-position switch is used in the electrical connections to the valve solenoids, 'saidswitchrbeing connected withis'prings arranged to normally 'setvthe switch in neutral position to open the Y`solenoid circuit'and said switch being manually moveable Yto twopositions Vto supply electrical currenttofop'erate 'the'valve solenoidsto selectively set the valve todeliver pressure fluid to each of the ends vof the cylinder-whiley simultaneously discharging fluid fromV the opposite end of the cylinder, and springs engaging the valve body 'to position Ythe body when the switch is in neutral position to connect yboth'endsof the cylinder with the fluid supply lines to lock the piston in fixed position in the cylinder. y f

`5. The ud drivemeeh-ani'smdened in claim l'in which va three-position control switch for the motor and flow valves is normally held in -a'neutral position by springs to cut orf 'the electrical power to the {motor 'and valve solenoids and said switch being manually movabie to two positions to set the valves to selectively deliver vp'ressu'reiluid to opposite ends of Vthe cylinder.

. to operate a solenoid `valve to move the cylinder piston in the Vopposite direction and ina third neutral position to .disconnect the electrical Ycircuit `from the solenoid valves, and .springs connected with the solenoid valves are arranged to set the valves to connect each end of the cylinder with the fluid supply line when the neutral position of the switch disconnects the electrical current from the solenoids whereby the operating duid is locked -in position at each end ofthe cylinder' by Ythe check valves in the supply lines. Y t 1 y Y 7. The fluid drive rmechanism defined `in claim 6 in which theswitch is arranged vformanualoperation to separately secure a reciprocation movement of the cylinder piston in one direction or the otherwhile vbeing held in a circuit closing position by an operator and -a spring mechanism connected with the switch to move `it into the neutral position when it is manually released.

References Cited in the le of this -patent UNITED STATES PATENTS 

